Wireless networks and systems are becoming increasingly popular. But wireless communications are constrained due to a lack of available, interference free spectrum that may be used for reliable communications within a geographic area.
To enhance the availability and reliability of interference free spectrum, procedures that are governed by regulatory agencies (e.g., the Federal Communications Commission (FCC) in the United States) have been developed for allocating and governing spectrum use. In the U.S., for example, the FCC licenses spectrum in a primary spectrum market to Commission licensees. A secondary market exists for the Commission licensees to sublease spectrum for use by other parties.
In the U.S., some spectrum may be used without a license in a spectrum sharing environment, but regulations on the spectrum may be imposed. For example, the FCC has eliminated analog television (TV) broadcasts in favor of digital TV broadcasts. This has freed spectrum channels for use by unlicensed radio systems to offer various services, such as mobile communications and Internet access. The freed spectrum is commonly referred to as TV white space. In the case of TV white space, the white space is comprised of unused TV spectrum between channel 2 and channel 51 (corresponding to 54 MHz to 698 MHz).
To avoid interference with digital TV broadcasts and other incumbent systems, such as wireless microphone systems, radios that use the TV white space are required to register and receive a channel map of available channels that may be used for the communications activity of the radio system. Current regulations require these radio systems to register every twenty-four hours. Also, for portable or mobile radios, if the radio moves into a new location, a new registration is required. Other regulations on the radios are present, such as transmitted power limits for different types of radios.